U.S. patent application number 13/058318 was filed with the patent office on 2011-06-16 for wireless transmitting device and wireless receiving device.
This patent application is currently assigned to PANASONIC CORPORATION. Invention is credited to Chie Ishida, Hong Tat Toh.
Application Number | 20110141908 13/058318 |
Document ID | / |
Family ID | 41668812 |
Filed Date | 2011-06-16 |
United States Patent
Application |
20110141908 |
Kind Code |
A1 |
Ishida; Chie ; et
al. |
June 16, 2011 |
WIRELESS TRANSMITTING DEVICE AND WIRELESS RECEIVING DEVICE
Abstract
A wireless transmitting device (10) comprises an MBMS data
transmitting unit (14) transmitting MBMS data, an MBMS control
information generating unit (13) generating MBMS control
information comprising access barring information, and a
transmitting unit (19). A wireless receiving device comprises a
data receiving unit receiving MBMS data, a control information
receiving unit receiving MBMS control information comprising access
barring information, an access class control unit performing access
class control on the basis of the MBMS control information, and an
RACH preamble transmitting unit transmitting an RACH preamble on
the basis of the result of the access class control. Thus the
wireless transmitting device and the wireless receiving device can
maintain an acceptable chance of successful connection
establishment by wireless communication devices that do not receive
MBMS, without reducing customer satisfaction in a cell that
provides MBMS.
Inventors: |
Ishida; Chie; (Kanagawa,
JP) ; Toh; Hong Tat; (Singapore, SG) |
Assignee: |
PANASONIC CORPORATION
OSAKA
JP
|
Family ID: |
41668812 |
Appl. No.: |
13/058318 |
Filed: |
July 31, 2009 |
PCT Filed: |
July 31, 2009 |
PCT NO: |
PCT/JP2009/003653 |
371 Date: |
February 9, 2011 |
Current U.S.
Class: |
370/241 ;
370/312 |
Current CPC
Class: |
H04W 48/02 20130101;
H04W 4/06 20130101 |
Class at
Publication: |
370/241 ;
370/312 |
International
Class: |
H04W 72/04 20090101
H04W072/04; H04L 12/26 20060101 H04L012/26 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 12, 2008 |
JP |
2008-207760 |
Claims
1-12. (canceled)
13. A wireless transmitting device comprising: a data transmitting
unit transmitting MBMS data; and a control information transmitting
unit transmitting MBMS control information comprising access
barring information.
14. The wireless transmitting device according to claim 13, wherein
the access barring information is information that enables
different access class controls for different MBMS services.
15. The wireless transmitting device according to claim 13, wherein
the access barring information is information that can comprise
priority of each of the MBMS services.
16. A wireless receiving device comprising: a data receiving unit
receiving MBMS data; a control information receiving unit receiving
MBMS control information comprising access barring information; an
access class control unit performing access class control on the
basis of the MBMS control information; and a random access preamble
transmitting unit transmitting a random access preamble on the
basis of a result of the access class control.
17. The wireless receiving device according to claim 16, wherein:
the MBMS data receiving unit uses a first frequency to receive
data; and the random access preamble transmitting unit uses the
first frequency to transmit a random access preamble when the
result of the access class control permits transmission of a random
access preamble, and uses a second frequency to transmit a random
access preamble when the result of the access class control
prohibits transmission of a random access preamble.
18. The wireless receiving device according to claim 17, wherein:
the control information receiving unit uses RRC protocol to further
receive information indicating a preferential frequency to be
preferentially used when a random access preamble cannot be
transmitted with the first frequency; and the random access
preamble transmitting unit transmits a random access preamble by
using the preferential frequency as the second frequency when the
result of the access class control prohibits transmission of a
random access preamble.
19. The wireless receiving device according to claim 17, further
comprising a priority determining unit determining priority of an
MBMS service and priority of a unicast service, wherein: when the
result of the access class control prohibits the use of the first
frequency to transmit an random access preamble, the priority
determining unit determines priority of an MBMS service currently
being received and priority of a unicast service and, if the
priority determining unit determines that the priority of the
unicast service is higher than the priority of the MBMS service,
the random access preamble transmitting unit uses the second
frequency to transmit a random access preamble.
20. A base station device comprising a wireless transmitting device
according to claim 13.
21. A terminal device comprising a wireless receiving device
according to claim 16.
22. A wireless communication system comprising a base station
device according to claim 20 and a terminal device comprising a
wireless receiving device comprising a data receiving unit
receiving MBMS data; a control information receiving unit receiving
MBMS control information comprising access barring information; an
access class control unit performing access class control on the
basis of the MBMS control information; and a random access preamble
transmitting unit transmitting a random access preamble on the
basis of a result of the access class control.
23. A wireless transmitting method comprising: a data transmitting
step of transmitting MBMS data; and a control information
transmitting step of transmitting MBMS control information
comprising access barring information.
24. A wireless receiving method comprising: a data receiving step
of receiving MBMS data; a control information receiving step of
receiving MBMS control information comprising access barring
information; an access class control step of performing access
class control on the basis of the MBMS control information; and a
random access preamble transmitting step of transmitting a random
access preamble on the basis of a result of the access class
control.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is based upon and claims the benefit of
priority from the prior Japanese Patent Application No.
2008-207760, filed on Aug. 12, 2008, the entire contents of which
are incorporated herein by reference.
TECHNICAL FIELD
[0002] The present invention relates to a wireless communication
technical field and, in particular, to a wireless transmitting
device that provides multimedia broadcast/multicast services
(hereinafter abbreviated as "MBMS") and a wireless receiving device
that receives the services.
BACKGROUND ART
[0003] When a wireless communication device in an idle state
initiates a connection setup procedure, the wireless communication
device needs to transmit a signal onto a network by following some
procedure in order to establish a dedicated channel between the
wireless communication device and a base station device. To
transmit the signal from the wireless communication device onto the
network, a Random Access Channel (hereinafter abbreviated as
"RACH"), which is an uplink common physical channel called, is
used.
[0004] The wireless communication device uses a preamble for
measuring the reception level of a Downlink Pilot Time Slot
(hereinafter abbreviated as "DwPTS"), detecting an RACH attempt,
and estimating the arrival timing to determine transmission power.
To avoid collisions between multiple wireless communication devices
that use the same slot at the same time, a sequence called
signature is used in a preamble. Preambles with different
signatures can be distinguished and detected when the preambles are
received at the same time. Accordingly, a collision can occur only
when both access slot and signature are identical and the
possibility of collision between preambles transmitted from
multiple wireless communication devices is generally low. However,
on rare occasions, preambles transmitted from multiple wireless
communication devices in a cell collide.
[0005] FIG. 14 is a diagram illustrating an access class control
operation for reducing the possibility of collision between
preambles. A base station 100 transmits access barring information,
which is an item of system information, through a Downlink Shared
Channel (hereinafter abbreviated as "DL-SCH") (S200), which is a
transport channel. The access barring information comprises a
threshold value (hereinafter referred to as "access probability
factor") which is used for access class control and determines
whether access is allowed or not, and a default value used for
calculating a barring timer.
[0006] A terminal 102 that received the access barring information
determines whether to connect to the base station 100 (S202). If
the terminal 102 connects to the base station 100 (YES at S202),
the terminal 102 performs access class control before transmitting
a random access preamble (hereinafter also referred to as "RACH
preamble"). Specifically, the terminal 102 compares a random value
generated locally by the terminal with the access probability
factor indicated in access barring information (S204). If the
random value is smaller than the access probability factor (YES at
S204), the terminal 102 transmits an RACH preamble (S206). On the
other hand, if the random value is greater than or equal to the
access probability factor (NO at S204), the terminal 102 calculates
the value of the barring timer (S208), initiates the barring timer
(S210), and waits until timeout of the barring timer. After the
timeout of the barring timer (S212), the terminal 102 proceeds to
step S204, where the terminal 102 compares a random value with the
access probability factor. The value of the barring timer is
calculated by multiplying a default value transmitted in system
information by a random value for the barring timer generated on
the terminal 102. Since different terminals 102 initiates
transmission of RACH preambles at different times in this way, the
possibility of collision between RACH preambles can be reduced.
Access class control is described in Patent Literature 1 and Non
Patent Literature 1 and 2.
CITATION LIST
Patent Literature
[0007] Patent Literature 1: Japanese Patent Application Publication
No. 2006-505979
Non Patent Literature
[0007] [0008] Non Patent Literature 1: 3GPP TS36.331 V8.2.0
"Evolved Universal Terrestrial Radio Access (E-UTRA) Radio Resource
Control (RRC)" [0009] Non Patent Literature 2: 3GPP TSG RAN WG2
meeting #61bis R2-081737, "Access Class barring enhancements to
support PPAC", NTT DoCoMo, Inc.
SUMMARY OF INVENTION
Problem to be Solved by the Invention
[0010] In the field of mobile communication, technical studies on
MBMS, which is broadcast or multicast services, are being
conducted. MBMS provides one-to-many communication rather than
one-to-one communication, where one base station device transmits
the same data (for example music data or video image data) to
multiple terminal devices at the same time.
[0011] In unicast communication, when a base station device uses
individual dedicated channels to broadcast information such as
streaming service information, the load on the wireless network
increases as the number of terminal devices that attempt to receive
the information increases. In contrast, MBMS has an advantage that
the number of terminal devices that can receive information can be
increased without increasing the load on the wireless network
because all terminal devices use the same channel to receive
information even when the number of terminal devices is increased.
MBMS-based services under consideration include traffic information
distribution, music distribution, news distribution, and sports
broadcast.
[0012] When a MBMS-based service is provided, many terminals will
attempt to access to a cell that provides the MBMS service. When
many terminals attempt to access a particular cell, the number of
RACH preambles transmitted from the terminals increases
accordingly. As a result, disadvantageously, transmission of RACH
preambles is blocked by access class control and even terminals
that do not receive the MBMS service cannot establish connections
to the base station. The problem can also arise among different
frequency bands provided by a single base station as well as on a
cell-by-cell basis.
[0013] FIG. 15 is a diagram illustrating an example of frequency
allocation by a base station that provides a MBMS service. In FIG.
15, one base station manages three different frequencies (f_x, f_y,
and f_mbms). Two frequencies (f_x and f_y) provide only a unicast
service and the other frequency (f_mbms) provides both unicast and
MBMS services. Here, if many terminals attempt to access the MBMS
service, it is to be anticipated that the frequency f_mbms that
provides the MBMS service will be crowded while the frequencies f_x
and f_y are relatively uncrowded.
[0014] The present invention has been made in light of these
circumstances and an object of the present invention is to provide
a wireless transmitting device and a wireless receiving device that
maintains an acceptable chance of successful connection
establishment of wireless communication devices that do not receive
MBMS in a cell that provides MBMS, without reducing user
satisfaction.
Means for Solving the Problems
[0015] A wireless transmitting device of the present invention
comprises a data transmitting unit transmitting MBMS data and a
control information transmitting unit transmitting MBMS control
information comprising access barring information.
[0016] A wireless receiving device of the present invention
comprises a data receiving unit receiving MBMS data, a control
information receiving unit receiving MBMS control information
comprising access barring information, an access class control unit
performing access class control on the basis of the MBMS control
information, and a random access preamble transmitting unit
transmitting a random access preamble on the basis of a result of
the access class control.
Advantages of the Invention
[0017] With this configuration, access barring information is
transmitted to terminals that receive an MBMS service but is not
provided to terminals that do not receive the MBMS service.
Accordingly, access class control is applied only to the terminals
that receive the MBMS. Since the terminals that receive the MBMS
service perform access class control on the basis of access barring
information included in MBMS control information, connection
establishment by the terminals that receive the MBMS service is
limited and accordingly an acceptable chance of successful
connection establishment by the terminals that do not receive the
MBMS service can be maintained.
[0018] There are other modes of the present invention as will be
described later. Therefore the disclosure of the present invention
is intended to provide part of the present invention and is not
intended to limit the scope of the present invention described and
claimed herein.
BRIEF DESCRIPTION OF DRAWINGS
[0019] FIG. 1 is a diagram illustrating a configuration of a base
station in a first embodiment.
[0020] FIG. 2 is a diagram illustrating a configuration of a
terminal in the first embodiment.
[0021] FIG. 3 is a diagram illustrating a network to which the
first embodiment is applied.
[0022] FIG. 4 is a diagram illustrating signaling operations in the
first embodiment.
[0023] FIG. 5 is a diagram illustrating an example of access
barring information.
[0024] FIG. 6 is a diagram illustrating an operation of a base
station in the first embodiment.
[0025] FIG. 7 is a diagram illustrating an operation of a terminal
in the first embodiment.
[0026] FIG. 8 is a diagram illustrating a configuration of a
terminal in a second embodiment.
[0027] FIG. 9 is a diagram illustrating signaling operations in the
second embodiment.
[0028] FIG. 10 is a diagram illustrating an operation of a terminal
in the second embodiment.
[0029] FIG. 11 is a diagram illustrating a configuration of a
terminal in a third embodiment.
[0030] FIG. 12 is a diagram illustrating signaling operations in
the third embodiment.
[0031] FIG. 13 is a diagram illustrating an operation of a terminal
in the third embodiment.
[0032] FIG. 14 is a diagram illustrating a conventional access
class control operation.
[0033] FIG. 15 is a diagram illustrating an example of frequency
allocation by a base station providing an MBMS service.
DESCRIPTION OF EMBODIMENTS
[0034] The present invention will be described in detail below.
Embodiments described below are illustrative only and various
modifications can be made to the present invention. Therefore,
specific configurations and functions disclosed below are not
intended to limit the scope of the claims.
[0035] A wireless transmitting device according to an embodiment
comprises a data transmitting unit transmitting MBMS data and a
control information transmitting unit transmitting MBMS control
information comprising access barring information.
[0036] With this configuration, access class control is applied
only to the terminals that receive an MBMS service because the
access barring information is transmitted only to the terminals
that receive an MBMS service and is not transmitted to terminals
that do not receive the MBMS service. By applying access class
control to the terminals that receive the MBMS service, an
acceptable chance of successful connection establishment by
terminals that do not receive the MBMS service can be
maintained.
[0037] The access barring information used by the wireless
transmitting device according to the present embodiment is
information that enables different access class controls for
different MBMS services.
[0038] With this configuration, the chance of successful connection
establishment can be controlled according to the type of MBMS
service that the terminal is receiving. For example, control can be
performed that allows a terminal that receives an unpopular MBMS
service to have a higher chance to establish a connection than a
terminal that receives a popular MBMS service.
[0039] The access barring information used by the wireless
transmitting device according to the present embodiment can include
priority of each individual MBMS service.
[0040] This configuration enables terminals to determine whether to
continue to receive an MBMS service or to establish another
connection, on the basis of the priority of each MBMS service.
[0041] A wireless receiving device according to the present
embodiment comprises a data receiving unit receiving MBMS data, a
control information receiving unit receiving MBMS control
information comprising access barring information, an access class
control unit performing access class control on the basis of the
MBMS control information, and an random access preamble
transmitting unit transmitting a random access preamble on the
basis of a result of the access class control.
[0042] With this configuration, since terminals that receive an
MBMS service perform access class control on the basis of access
barring information included in MBMS control information, the
chance of connection establishment by the terminals that receive
the MBMS service is restricted and accordingly an acceptable chance
of successful connection establishment by terminals that do not
receive an MBMS service can be maintained.
[0043] In the wireless receiving device according to the present
embodiment, the MBMS data receiving unit uses a first frequency to
receive data, and the random access preamble transmitting unit uses
the first frequency to transmit a random access preamble when the
result of the access class control permits transmission of a random
access preamble, and uses a second frequency to transmit a random
access preamble when the result of the access class control
prohibits transmission of a random access preamble.
[0044] With this configuration, a random access preamble is
transmitted with the second frequency different from the first
frequency with which the MBMS service is provided. Since different
frequencies, the first and second frequencies, are used for
transmitting random access preambles, the probability of collision
between random access preambles can be reduced.
[0045] In the wireless receiving device according to the present
embodiment, the control information receiving unit uses RRC
protocol to further receive information indicating a preferential
frequency to be preferentially used when a random access preamble
cannot be transmitted with the first frequency, and the random
access preamble transmitting unit transmits a random access
preamble by using the preferential frequency as the second
frequency when the result of the access class control prohibits
transmission of a random access preamble.
[0046] This configuration enables a base station to set a
preferential frequency for a terminal, thereby controlling the
frequency used for transmitting a random access preamble.
[0047] The wireless receiving device according to the present
embodiment further comprises a priority determining unit
determining priority of an MBMS service and priority of a unicast
service, wherein when the result of the access class control
prohibits the use of the first frequency to transmit an random
access preamble, the priority deteinfining unit determines priority
of an MBMS service currently being received and priority of a
unicast service and, if the priority determining unit determines
that the priority of the unicast service is higher than the
priority of the MBMS service, the random access preamble
transmitting unit uses the second frequency to transmit a random
access preamble.
[0048] With this configuration, when the priority of the unicast
service is higher, the wireless receiving device can switch to the
second frequency to quickly start transmitting the random access
preamble; when the priority of the MBMS service is higher, the
wireless receiving device can continue using the first frequency to
receive the MBMS service at the expense of the time required to
establish a connection.
[0049] A base station device of the present embodiment has the
configuration of the wireless transmitting device described above.
A terminal device of the present embodiment has the configuration
of the wireless receiving device described above. A wireless
communication system of the present embodiment comprises the base
station device and the terminal device described above.
[0050] With this configuration, the base station device provides an
MBMS service and the problem associated with the MBMS service that
it takes a long time to establish a connection can be solved.
[0051] A wireless transmitting method according to the present
embodiment comprises a data transmitting step of transmitting MBMS
data and a control information transmitting step of transmitting
MBMS control information comprising access barring information.
[0052] With this configuration, like the wireless transmitting
device of the present embodiment described above, the method
applies access class control to terminals that receive an MBMS
service to maintain an acceptable chance of successful connection
establishment by terminals that do not receive the MBMS
service.
[0053] A wireless receiving method according to the present
embodiment comprises a data receiving step of receiving MBMS data,
a control information receiving step of receiving MBMS control
information comprising access barring information, an access class
control step of performing access class control on the basis of the
MBMS control information, and a random access preamble transmitting
step of transmitting a random access preamble on the basis of a
result of the access class control.
[0054] With this configuration, like the wireless receiving device
of the present embodiment described above, the method applies
access class control to terminals that receive an MBMS service on
the basis of access barring information included in MBMS control
information. Therefore, transmission of random access preambles by
the terminals that receive the MBMS service can be restricted to
maintain an acceptable chance of successful connection
establishment by terminals that do not receive the MBMS
service.
[0055] Wireless transmitting devices and wireless receiving devices
according to embodiments of the present invention will be described
below in detail with reference to drawings. A wireless
communication system comprising a base station device (hereinafter
referred to as "base station") and terminal devices (hereinafter
referred to as "terminals") will be taken as an example. In the
following example, the base station represents a wireless
transmitting device and the terminals represent wireless receiving
devices. In the embodiments described below, elements having like
functions will be given like numerals and repeated description of
those elements will be omitted.
[0056] The embodiments will be described with respect to Long Term.
Evolution (LTE), System Architecture Evolution (SAE), and MBMS,
which are mobile communication technologies standardized in 3GPP.
However, the present invention is not limited to the standards in
3GPP but is also applicable to wireless access technologies such as
WLAN (Wireless Local Area network), WiMAX (Worldwide
Interoperability for Microwave Access) in IEEE 802.16, IEEE
802.16e, and IEEE 802.16m, and 3GPP2, the fourth generation mobile
communication technology, and other technologies.
First Embodiment
[0057] FIG. 1 is a diagram illustrating a configuration of a base
station 10 according to a first embodiment. FIG. 2 is a diagram
illustrating a configuration of a terminal 30 according to the
first embodiment. A configuration of a network to which the base
station 10 and the terminal 30 of the first embodiment are applied
will be described first before describing the base station 10 and
the terminal 30 in detail with reference to FIGS. 1 and 2.
[0058] FIG. 3 is a diagram illustrating a configuration of the
network relating to the first embodiment of the present invention.
The network illustrated in FIG. 3 comprises terminals (User
Equipments: UE) 30, base stations (Evolved Nodes B, eNB) 10, an
MBMS control device (MBMS Control Entity: MCE) 50, and a core
network (Evolved Packet Core: EPC) 51.
[0059] Each of the base stations 10 allocates and manages wireless
resources and functions as an access point of a wireless access
network for terminals 30. The base station 10 receives information
transferred from the terminals 30 through uplinks and transfers
data to the terminals 30 through downlinks.
[0060] The MCE 50 manages multiple base stations 10 and allocates
physical resource blocks to MBMS services. The EPC 51, which is the
core of the mobile communication network, distributes MBMS contents
and controls MBMS data and sessions.
[0061] A configuration of the base station 10 will be described
with reference to FIG. 1. The base station 10 comprises an
MBMS-related information storage 11, a random-access-related
information storage 12, an MBMS control information generating unit
13, an MBMS data transmitting unit 14, a system information
transmitting unit 15, and a unicast data processing unit 16, as
components for transmitting data to the terminals 30. The base
station 10 comprises an RACH processing unit 17 and a data
processing unit 18 as components that process data received from
terminals 30.
[0062] The MBMS-related information storage 11 stores control
information and data relating to an MBMS service. The
random-access-related information storage 12 stores information
relating to random access such as access barring information.
[0063] The MBMS control information generating unit 13 reads out
access barring information from the random-access-related
information storage 12 and reads out control information relating
to an MBMS service from the MBMS-related information storage 11.
The MBMS control information generating unit 13 generates MBMS
control information such as service notification information and
scheduling information on the basis of the read-out information and
outputs the MBMS control information to a transmitting unit 19. The
MBMS data transmitting unit 14 processes MBMS data read-out from
the MBMS-related information storage 11 and outputs the processed
MBMS data to the transmitting unit 19.
[0064] The unicast data processing unit 16 outputs unicast data to
the transmitting unit 19. The system information transmitting unit
15 outputs system information to the transmitting unit 19.
[0065] The transmitting unit 19 sends out information input from
the MBMS control information generating unit 13, the unicast data
processing unit 16, the MBMS data transmitting unit 14, and the
system information transmitting unit 15 through an antenna 21.
[0066] The RACH processing unit 17 processes an RACH preamble input
from a receiving unit 20. The data processing unit 18 processes
data input from the receiving unit 20.
[0067] The receiving unit 20 receives an RACH preamble transmitted
from a terminal 30 and data transmitted from a terminal 30 and the
core network and outputs the RACH preamble and the data to the RACH
processing unit 17 and the data processing unit 18,
respectively.
[0068] A configuration of the terminal 30 will be described below
with reference to FIG. 2. The terminal 30 comprises a receiving
unit 32 receiving data transmitted from a base station 10 through
an antenna 31 and a transmitting unit 33 transmitting data to a
base station 10. The receiving unit 32 receives system information,
MBMS control information, MBMS data, and unicast data transmitted
from a base station 10. The receiving unit 32 inputs the system
information and the MBMS control information it received to a
control unit 35 and inputs the MBMS data and the unicast data it
received to a data reproducing unit 34.
[0069] The data reproducing unit 34 reproduces MBMS data and
unicast data input from the receiving unit 32. The control unit 35
extracts random-access-control-related information and system
information from MBMS control information input from the receiving
unit 32 and outputs the random-access-control-related information
and the system information to a storage 36. If access barring
information is included in the random-access-control-related
information, the control unit 35 instructs an access class control
unit 37 to perform access class control.
[0070] The access class control unit 37 performs access control of
RACH preamble transmission. Specifically, the access class control
unit 37 generates a random value in response to an instruction from
the control unit 35 and compares the random value with an access
probability factor. If the comparison shows that the random value
is greater than or equal to the access probability factor, the
access class control unit 37 instructs a timer control unit 38 to
run a barring timer; if the comparison shows that the random value
is smaller than the access probability factor, the access class
control unit 37 instructs an RACH preamble generating unit 39 to
generate an RACH preamble.
[0071] The timer control unit 38 calculates and runs a barring
timer in response to an instruction from the access class control
unit 37 and prohibits transmission of an RACH preamble until the
timeout of the barring timer.
[0072] The RACH preamble generating unit 39 generates an RACH
preamble in response to an instruction from the access class
control unit 37 and outputs the RACH preamble to the transmitting
unit 33. A data transmitting unit 40 outputs data to be transmitted
to a base station 10 to the transmitting unit 33.
[0073] The transmitting unit 33 transmits an RACH preamble input
from the RACH preamble generating unit 39 and data input from the
data transmitting unit 40 to the base station 10.
[0074] FIG. 4 is a diagram illustrating signaling operations of a
base station 10 and a terminal 30 according to the first embodiment
of the present invention. The terminal 30 receives system
information from the base station 10 through a downlink shared
channel (DL-SCH), which is a transport channel (S10). It is assumed
here that access barring information is not included in the
transmitted system information.
[0075] The terminal 30 receives a list of MBMS services available
in the cell from the base station 10 through an MBMS control
channel (hereinafter abbreviated as "MCCH"), which is a logical
channel (S12). The MCCH has been mapped to one of a DL-SCH or a
multicast channel (hereinafter abbreviated as "MCH"), which are
transport channels.
[0076] Here, if the base station 10 has determined to apply access
class control to the terminal 30, access barring information is
transmitted through the MCCH at the same time as the list of MBMS
services available in the cell (S12). The access barring
information comprises an access timer flag indicating whether
access class control is to be performed or not, an access
probability factor used for access class control, and a default
value. If the barring timer flag is on, the terminal, if receives
an MBMS service, performs access class control prior to
transmission of an RACH preamble; if the barring timer flag is off,
the terminal does not perform access class control. The access
probability factor and the default value are set for all MBMS
services in common. Alternatively, an access probability factor and
a default value may be set individually for each MBMS service.
[0077] FIG. 5 is a diagram illustrating another example of access
barring information. In this example, the access barring
information is a barring timer flag associated with each MBMS
service. If the barring timer flag is on, an access probability
factor and a default value are also associated with the MBMS
service as data used for performing access class control. According
to these items of access barring information, access class control
that differs from one MBMS service to another can be performed.
[0078] Referring again to FIG. 4, the description of the signaling
will be continued. If an MBMS service that the terminal 30 user
wants to receive (here, MBMS service #1) is on the list, the
terminal 30 in an idle state establishes a connection to the base
station 10, enters an active state (S14) and transmits a service
request for MBMS service #1 to the base station 10 (S16).
[0079] The base station 10 receives the service request from the
terminal 30 and sets up a wireless bearer for the terminal 30 to
receive that service (S18). The terminal 30 receives MBMS service
#1 through the wireless bearer set up by the base station 10 (S20).
Then the base station 10 transmits an RRC connection release
message to the terminal 30 (S22). When the terminal 30 receives the
message, the terminal 30 returns to the idle state (S24). In
consequence, the terminal 30 enters a state in which the terminal
30 is only receiving MBMS service #1. That is, the terminal 30
receives the MBMS service in the idle state. If the desired MBMS
service (MBMS service #1) has already been transmitted from the
base station 10 to the terminal 30, steps S14, S16 and S18 would be
omitted.
[0080] Then, the terminal 30, which is receiving MBMS service #1
(S26), determines whether or not an attempt has been made on the
terminal 30 to establish a connection to the base station 10 to
cause the terminal 30 to enter the active state (S28). For example,
if an operation to initiate a call or send mail has been performed
on the terminal 30, the terminal 30 determines that an attempt has
been made to connect to the base station 10 to cause the terminal
30 to enter the active state. In the example illustrated in FIG. 4,
if an attempt has been made to connect to the base station 10 (YES
at S28), the terminal 30 performs access class control. The
terminal 30 compares a random value generated locally on the
terminal 30 with the access probability factor to determine whether
or not the random value is smaller than the access probability
factor (S30). If the random value is smaller than the access
probability factor (YES at S30), the terminal 30 transmits an RACH
preamble (S32).
[0081] If the random value is greater than or equal to the access
probability factor (NO at S30), then the terminal 30 calculates the
value of the barring timer (534) and initiates the barring timer
(S36). The terminal 30 waits until timeout of the barring timer.
Upon timeout of the barring timer, the terminal 30 performs step
S30, where the terminal 30 compares a random value with the access
probability factor again.
[0082] FIG. 6 is a diagram illustrating an operation of the base
station 10 that implements signaling between the base station 10
and the terminal 30 described above. The base station 10 transmits
system information to the terminal 30 (S40). The base station 10
generates MBMS control information including access barring
information (S42) and transmits the generated MBMS control
information to the terminal 30 (S44).
[0083] Then the base station 10 determines whether or not a service
request for an MBMS service has been transmitted from a terminal 30
(S46). If a service request for an MBMS service has been
transmitted from a terminal 30, the base station 10 sets up a
wireless bearer for the terminal 30 to receive the MBMS service
(S48) and transmits MBMS data (S50).
[0084] FIG. 7 is a diagram illustrating an operation of the
terminal 30 that implements signaling between the base station 10
and the terminal 30 described above. When the terminal 30 receives
MBMS control information (S60), the terminal 30 determines whether
or not access class barring information is included in the MBMS
control information (S62). If access class barring information is
not included (NO at S62), the terminal 30 transmits an RACH
preamble when attempting to establish a connection to the base
station 10 (S64).
[0085] If access class barring information is included (YES at
S62), the terminal 30 performs access class control prior to
transmission of the RACH preamble. First, the terminal 30 compares
a random value that the terminal 30 has generated with the access
probability factor contained in the MBMS control information to
determine whether or not the random value is smaller than the
access probability factor (S66). If the comparison shows that the
random value is smaller than the access probability factor (YES at
S66), the terminal 30 transmits the RACH preamble (S68).
[0086] If the random value is greater than or equal to the access
probability factor (NO at S66), the terminal 30 calculates the
value of the barring timer (S70). The value of the barring timer is
calculated by multiplying the default value of the barring timer
specified in the access class barring information included in the
MBMS control information by a random value generated locally on the
terminal 30. The terminal 30 initiates the calculated barring timer
(S72) and prohibits transmission of the RACH preamble while the
barring timer is running. Upon timeout of the barring timer (S74),
the terminal 30 compares a random value locally generated on the
terminal with the access probability factor again (S66). The
configurations and operations of the base station 10 and the
terminal 30 of the first embodiment have been described thus
far.
[0087] Since the base station 10 of the first embodiment specifies
in the MBMS control information whether access class control is to
be performed or not, only the terminals 30 that receive an MBMS
service perform access class control when the terminals 30 transmit
an RACH preamble. Accordingly, collisions between RACH preambles
can be reduced without affecting terminals 30 that do not receive
the MBMS service.
[0088] Furthermore, since access barring information is transmitted
in MBMS control information, the access barring information can be
provided only to the terminals that receive the MBMS service with a
simple configuration.
[0089] While the present embodiment has been described with respect
to an example in which access barring information includes a
barring timer flag indicating whether access class control is to be
performed for each MBMS service, MBMS control information that does
not include a barring timer flag may be used. If access barring
information does not include a barring timer flag, terminals 30
that receive any of the MBMS service on the list will perform
access class control.
Second Embodiment
[0090] A second embodiment of the present invention will be
described below. A base station 10 of the second embodiment has the
same configuration as the base station 10 of the first
embodiment.
[0091] FIG. 8 is a diagram illustrating a configuration of a
terminal 30a according to the second embodiment. The configuration
of the terminal 30a of the second embodiment is basically the same
as the configuration of the terminal 30 of the first embodiment,
except that the terminal 30a of the second embodiment comprises a
frequency changing unit 41 which changes frequency with which an
RACH preamble is transmitted.
[0092] An access class control unit 37 generates a random value in
response to an instruction from a control unit 35 and compares the
value with an access probability factor. If the comparison shows
that the random value is smaller than the access probability
factor, the access class control unit 37 instructs an RACH preamble
generating unit 39 to generate an RACH preamble. If the random
value is greater than or equal to the access probability factor,
the access class control unit 37 instructs the frequency changing
unit 41 to change frequency.
[0093] When there is preferential frequency information output from
a storage 36, the frequency changing unit 41 switches to that
frequency. When there is not preferential frequency information,
the frequency changing unit 41 reselects a frequency on the basis
of frequency information included in system information output from
the storage 36 indicating the frequency to be preferentially
selected by the terminal 30a.
[0094] FIG. 9 is a diagram illustrating signaling between a
terminal 30a and a base station 10 in the second embodiment. In
FIG. 9, it is assumed that the base station 10 manages multiple
frequencies (f_x and f_mbms) and the terminal 30a in an idle state
is camped on frequency f_x and receiving system information and
paging (S80).
[0095] The terminal 30a receives the system information through a
downlink shared channel (DL-SCH), which is a transport channel,
with frequency f_x (S82). In the system information, frequency
information indicating a frequency to be preferentially selected by
the terminal 30a when the terminal 30a reselects a cell and
information indicating a frequency that supports an MBMS service is
transmitted (S84). Here, it is assumed that access barring
information has not been transmitted in the system information.
[0096] When the terminal 30a receives the MBMS supporting frequency
information in the system information, the terminal 30a camps on
the MBMS supporting frequency (f_mbms) from the current frequency
(f_x) (S86). As a result, the terminal 30a receives system
information and paging by using frequency f_mbms (S88).
[0097] The terminal 30a receives a list of MBMS services available
in the cell from the base station 10 through an MCCH, which is a
logical channel (S90). The MCCH has been mapped to one of a DL-SCH
or MCH, which are transport channels. Here, if the base station 10
has determined to apply access class control to the MBMS terminal
30a, the base station 10 transmits access barring information to
the terminal 30a through the MCCH at the same time as the list of
MBMS services available in the cell. The access barring information
is the same as the access barring information transmitted from the
base station 10 in the first embodiment.
[0098] If an MBMS service that the terminal 30a user wants to
receive (here MBMS service #1) is on the list, the terminal 30a in
an idle state establishes a connection to the base station 10 to
enter an active state (S92) and transmits a service request for
MBMS service #1 to the base station 10 (S94). When the base station
10 receives the service request from the terminal 30a, the base
station 10 sets up a wireless bearer for the terminal 30a to
receive that service (S96). The terminal 30a receives MBMS service
#1 through the wireless bearer set up by the base station 10
(S98).
[0099] Then, the base station 10 transmits an RRC connection
release message to the terminal 30a (S100). When the terminal 30a
receives the message, the terminal 30a returns to the idle state
(S104). The RRC connection release message indicates a frequency
(here, f_x) that the terminal 30a is to preferentially select after
the terminal 30a enters the idle state. The aim of this is to
allocate different frequencies among terminals 30a that attempt to
connect to the base station 10, thereby avoiding overloading any
one frequency with many connections. Here, however, the terminal
30a does not switch to the preferential frequency (f_x) specified
by the base station 10 but remains at the MBMS supporting frequency
(f_mbms) in order to receive the MBMS service. The terminal 30a
stores the preferential frequency (f_x) specified by the base
station 10 in a storage 36 (S102). If the desired MBMS service
(MBMS service #1) has already been transmitted from the base
station 10, steps S92, S94, S96 and S100 would be omitted.
[0100] In the example illustrated in FIG. 9, the terminal 30a,
which is receiving MBMS service #1, determines whether the terminal
30a is to establish a connection to the base station 10 to enter
the active state (S108). If the terminal 30a determines that the
terminal 30a is to connect to the base station 10 (YES at S108),
the terminal 30a performs access class control.
[0101] The terminal 30a compares a random value locally generated
on the terminal 30a with the access probability factor to determine
whether the random value is smaller than the access probability
factor (S110). If the random value is smaller than the access
probability factor (YES at S110), the terminal 30a transmits an
RACH preamble (S112).
[0102] If the random value is greater than or equal to the access
probability factor (NO at S110), the terminal 30a reads out
information indicating the preferential frequency (f_x) from the
storage 36, switches to the read out preferential frequency (f_x)
(S114), and transmits an RACH preamble with the preferential
frequency (f_x) (S116). If information indicating the preferential
frequency (f_x) is not stored in the storage 36, the terminal 30a
reselects a frequency on the basis of information transmitted in
the system information that indicates a frequency to be
preferentially selected by the terminal 30a.
[0103] FIG. 10 is a diagram illustrating an operation of the
terminal 30a that implements signaling between the terminal 30a and
the base station 10 described above. When the terminal 30a receives
MBMS control information (S130), the terminal 30a determines
whether or not access class barring information is included in the
MBMS control information (S132). If access class barring
information is not included (NO at S132), the terminal 30a
transmits an RACH preamble (S134).
[0104] If access class barring information is included (YES at
S132), the terminal 30a performs access class control. In the
access class control, the terminal 30a first generates a random
value and compares the generated random value with the access
probability factor (S136). If the random value is smaller than the
access probability factor (YES at S136), the terminal 30a transmits
an RACH preamble (S138).
[0105] The random value is greater than or equal to the access
probability factor (NO at S136), the terminal 30a changes
frequency. The terminal 30a determines whether or not a
preferential frequency has been specified in the RRC connection
release message when the RRC connection has been released by the
base station 10. If a preferential frequency is specified, that is,
a preferential frequency is stored in the storage 36 (YES at S140),
the terminal 30a switches to that frequency (S142) and transmits an
RACH preamble (S146).
[0106] If a preferential frequency is not specified, that is, a
preferential frequency is not stored in the storage 36 (NO at
S140), the terminal 30a reselects a frequency on the basis of
information included in the system information that indicates a
frequency to be preferentially selected by the terminal 30a (S144).
After switching to the newly selected frequency, the terminal 30a
transmits an RACH preamble (S146). The configurations and
operations of the base station 10 and the terminal 30a of the
second embodiment have been described thus far.
[0107] Since each of the terminals 30a of the second embodiment
uses a different preferential frequencies specified individually by
the base station 10 when a random value generated locally on the
terminal 30a in access class control is smaller than an access
probability factor, congestion on a particular frequency can be
avoided and collisions between RACH preambles can be reduced.
[0108] In the embodiment described above, if the terminal 30a is
originally in a cell that supports MBMS, MBMS supporting frequency
does not need to be transmitted in system information.
Third Embodiment
[0109] A base station 10 and a terminal 30b of a third embodiment
will be described below. The base station 10 and the terminal 30b
in the third embodiment have basically the same configurations as
the base station 10 and the terminal 30a in the second embodiment.
The terminal 30b of the third embodiment differs from the terminal
30a of the second embodiment in that the terminal 30b of the third
embodiment performs RACH preamble access control depending on the
priorities of MBMS services and a unicast services.
[0110] FIG. 11 is a diagram illustrating a configuration of the
terminal 30b of the third embodiment. The terminal 30b of the third
embodiment comprises a priority determining unit 42 and a timer
control unit 38 in addition to the components of the terminal 30a
of the second embodiment.
[0111] An access class control unit 37 generates a random value in
response to an instruction from a control unit 35 and compares the
random value with an access probability factor. If the comparison
shows that the random value is greater than or equal to the access
probability factor, the access class control unit 37 instructs the
priority determining unit 42 to determine the order of priorities;
if the random value is smaller than the access probability factor,
the access class control unit 37 instructs an RACH preamble
generating unit 39 to generate an RACH preamble.
[0112] The priority determining unit 42 compares the priority of
the unicast service and the priority of MBMS services. If the
priority of the unicast service is higher, the priority determining
unit 42 instructs a frequency changing unit 41 to change frequency.
If the priority of the MBMS services is higher, the priority
determining unit 42 instructs the timer control unit 38 to run a
timer.
[0113] If information indicating a preferential frequency is stored
in a storage 36, the frequency changing unit 41 switches to that
frequency. If information indicating a preferential frequency is
not stored in the storage 36, the frequency changing unit 41 reads
out system information from the storage 36 and reselects a
frequency on the basis of information in the read-out system
information that indicates a frequency to be preferentially
selected by the terminal 30b.
[0114] The timer control unit 38 calculates and runs a barring
timer in response to an instruction from the priority determining
unit 42 and prohibits transmission of the RACH preamble until
expiration of the barring timer.
[0115] FIG. 12 is a diagram illustrating signaling operations of a
base station 10 and a terminal 30b according to the third
embodiment. The operations are the same as the signaling operations
in the second embodiment until the terminal 30b receives an MBMS
service (S80 to S106).
[0116] When the terminal 30b, which is receiving MBMS service #1,
attempts to establish a connection to the base station 10 and
switches to an active state (YES at S108), the terminal 30b
performs access class control. In the access class control, the
terminal 30b first compares a random value locally generated on the
terminal 30b with an access probability factor to determine if the
random value is smaller than the access probability factor (S110).
If the random value is smaller than the access probability factor
(YES at S110), the terminal 30b transmits an RACH preamble
(S112).
[0117] If the random value is greater than or equal to the access
probability factor (NO at S110), the terminal 30b compares the
priority of the unicast service with the priority of the MBMS
services (S113). The priorities of the services may be set by the
user in advance or by the base station 10. If the comparison
between the priorities of the services shows that the priority of
the unicast service is higher (YES at S113), the terminal 30b reads
out information indicating a preferential frequency (f_x) from the
storage 36, switches to the read-out preferential frequency (f_x)
(S114), and transmits an RACH preamble with the frequency (f_x)
(S116). If information indicating a preferential frequency is not
stored in the storage 36, the terminal 30b reselects a cell on the
basis of frequency information transmitted in system information
that indicates a frequency to be preferentially selected by the
terminal 30b.
[0118] If the priority of the MBMS services is higher than that of
the unicast service (NO a S113), the terminal 30b calculates the
value of a barring timer (S118), initiates the barring timer
(S120), and waits until the timeout of the barring timer. Upon the
timeout of the barring timer (S122), the terminal 30b returns to
step S110, where a random value is compared with and the access
probability factor.
[0119] FIG. 13 is a diagram illustrating an operation of the
terminal 30b that implements signaling between the terminal 30b and
the base station 10 described above. When the terminal 30b receives
MBMS control information (S130), the terminal 30b determines
whether or not access barring information is included in the MBMS
control information (S132). If access class barring information is
not included (NO at S132), the terminal 30b transmits an RACH
preamble (S134).
[0120] If access class barring information is included (YES at
S132), the terminal 30b performs access class control. In the
access class control, the terminal 30b locally generates a random
value first and compares the random value with the access
probability factor to determine whether the random value is smaller
than the access probability factor (S136). If the random value is
smaller than the access probability factor (YES at S136), the
terminal 30b transmits an RACH preamble (S138).
[0121] If the random value is greater than or equal to the access
probability factor (NO at S136), the terminal 30b compares the
priorities of the unicast service and the MBMS services (S139). If
the priority of the unicast service is higher (YES at S139), the
terminal 30b changes frequency. The terminal 30b determines whether
or not a preferential frequency has been specified in an RRC
message by the base station 10 when the RRC connection has been
released (S140). If a preferential frequency is specified (YES at
S140), the terminal 30b switches to the frequency (S142) and
transmits an RACH preamble (S146).
[0122] If a preferential frequency is not specified (NO at S140),
the terminal 30b reselects a frequency on the basis of information
in system information that indicates a frequency to be
preferentially selected by the terminal 30b (S144). The terminal
30b switches to the newly selected frequency and then transmits an
RACH preamble (S146).
[0123] If the priority of the MBMS services is higher (NO at S139),
the terminal 30b calculates the value of a barring timer (S148).
The value of the barring timer is calculated by multiplying the
default value of the barring timer specified in access class
barring information in MBMS control information by a random value
generated locally on the terminal. The terminal 30b runs the
calculated barring timer (S150) and prohibits transmission of an
RACH preamble while the barring timer is running. Upon timeout of
the barring timer (S152), the terminal 30b again compares a random
value generated locally on the terminal with the access probability
factor (S136). The configurations and operations of a base station
10b and a terminal 30b of the third embodiment have been described
thus far.
[0124] According to the third embodiment, each terminal 30b can
select and give priority to transmission of an RACH preamble or
reception of the MBMS service, on the basis of which of the
priorities of the unicast service and the MBMS services is
higher.
[0125] When RACH preamble transmission is selected the RACH
preamble is transmitted with a preferential frequency specified by
the base station 10 and therefore collisions between RACH preambles
can be reduced.
[0126] In the embodiment described above, a priority may be set for
each MBMS service and the set priority may be compared with the
priority of the unicast service. This enables more detailed control
in which for example when the service being received is service
"A", the unicast service is given priority over MBMS service "A"
and switching is made to the unicast service, or when the service
being received is MBMS service "B", MBMS service "B" is given
priority over the unicast service to continue receiving MBMS
service "B".
[0127] In the embodiment described above, RACH preamble access
control may be performed according to, for example, the amount of
downlink resources required by the terminal 30b. For example,
instead of the comparison between the priorities of MBMS and
unicast services at S139 in FIG. 13, the amount of downlink
resources currently being used by the terminal 30b may be compared
with an amount of resources specified at the base station 10 and,
if the amount of downlink resources being used is greater than the
specified amount, the value of the barring timer may be calculated
(S148). If the amount of downlink resources being used is smaller
than the specified amount, frequency may be changed. Alternatively,
a combination of the amount of downlink resources being used and
the priorities of MBMS and unicast services may be used.
[0128] In the embodiment described above, both of the unicast
service and the MBMS service may be performed. For example, if the
unicast service and the MBMS service have the same priority such as
"high priority", or if the difference in priority between the
unicast service and the MBMS service is small, both of the unicast
and MBMS services may be performed.
[0129] While embodiments of the present invention that are
preferable as of the date of preparation of this application have
been described above, it will be understood that various
modifications can be made to the embodiments and it is intended to
cover in the attached claims all such modifications and variations
as fall within the true spirit and scope of the present
invention.
INDUSTRIAL APPLICABILITY
[0130] The present invention has the advantageous effect of making
it possible to provide an MBMS service while maintaining an
acceptable chance of successful connection establishment by
terminals that do not receive MBMS services. The present invention
is useful in applications such as base stations providing MBMS
services and terminals receiving the MBMS services.
REFERENCE SIGNS LIST
[0131] 10 Base station [0132] 11 MBMS-related information storage
[0133] 12 Random-access-related information storage [0134] 13 MBMS
control information generating unit [0135] 14 MBMS data
transmitting unit [0136] 15 System information transmitting unit
[0137] 16 Unicast data processing unit [0138] 17 RACH processing
unit [0139] 18 Data processing unit [0140] 19 Transmitting unit
[0141] 20 Receiving unit [0142] 21 Antenna [0143] 30 Terminal
[0144] 31 Antenna [0145] 32 Receiving unit [0146] 33 Transmitting
unit [0147] 34 Data reproducing unit [0148] 35 Control unit [0149]
36 Storage [0150] 37 Access class control unit [0151] 38 Timer
control unit [0152] 39 RACH preamble generating unit [0153] 40 Data
transmitting unit
* * * * *